American geneticist Hermann Muller's work introduced the conceptual and empirical basis for modern molecular biology. Breeding huge numbers of the fruit fly Drosophila melanogaster, he demonstrated that exposure to X rays can cause mutations in genes and chromosomes of living cells, and warned that radiation could cause mutations in the human gene pool as well. His research won Muller the Nobel Prize for Physiology or Medicine in 1946.

Raised in Harlem, Muller attended Morris High in the Bronx, where he and two friends founded what may have been America's first high school science club, in 1906. Acing the entrance exam, he was awarded a small scholarship at Columbia College, and earned the rest of his tuition working 14-hour days in the summer, as a bank errand boy and hotel clerk. In addition to his class load, he spent his spare time reading advanced textbooks on genetics, biology and physiology. During his grad school years, he supported himself by teaching English to immigrants in night school.

He was a man of political convictions and an argumentative disposition, which severely hindered his career. Hired by Julian Huxley at Rice University, he did not last long there. He spent a dozen years at the University of Texas, where he became active with peace groups and served as faculty sponsor for the National Students League, a leftist student group under observation by the FBI. After Muller wrote an article in group's newsletter, he was advised by UT President Harry Yandell Benedict that he would be subject to an investigation and likely expulsion, so Muller left Texas.

He spent a year studying at one of the world's most prestigious genetics labs, the Institute for Brain Research in Berlin. It was an unfortunate time to visit Germany, however -- Hitler took power almost as soon as Muller arrived. The scholar was assigned a secretary, Regina Wender, but she was Jewish and thus faced sneers and scrutiny every time she entered the building. After a few months she fled to Russia, and Muller, feeling he could neither stay in Germany nor return to America, followed her to the Academy of Sciences of the U.S.S.R. But under Stalin's rule, the false genetic theories of Trofim Lysenko held sway, and some of Muller's colleagues were imprisoned, others disappeared, before Mueller was able to relocate to the University of Edinburgh.

Returning to America as World War II swept the globe, Muller was seen both as one of the world's foremost geneticists, and as a political pariah. To right-wingers, he was suspect for his political statements and time in the Soviet Union. To left-wingers, he was seen as something of a back-stabber, for his honest but outspoken assessment of Stalin's cruelty. Despite his inarguable brilliance, Muller bounced from college to college before finally finding tenure at Indiana University, where Carl Sagan was among Muller's undergraduate students, and where Muller won his Nobel Prize, for work conducted years earlier in Texas.

Regina Wender, Muller's secretary in Germany and later in Russia, married a biophysicist and emigrated to America, where her son grew up to be noted chess master and nutcase Bobby Fischer.